Method and apparatus for producing a casting having a satisfactory surface with a continuous casting operation

ABSTRACT

A method for producing a casting wherein the casting is solidified in a continuous casting machine and treated by medium scarfing while maintaining the surface temperature at 500* to 900*C, and thereafter, cooled forceably to bring the surface temperature below 400*C.

United States Patent Nozaki June 17 1975 METHOD AND APPARATUS FOR 3,354,002 11/1967 PRODUCING A CASTING HAVING A 15 32 SATISFACTORY SURFACE WITH A ggg x CONTINUOUS CASTING OPERATION [75] Inventor: Teruhiko Nozaki, Nishinomiya, FOREIGN PATENTS OR APPLICATIONS Japan I.9I 1,702 9/1970 Germany I48/915 [73] Assignee: Kobe Steel, Inc., Kobe, Japan Primary Examiner c Lanham [22] Filed: Sept. 7, 1973 Assistant Examiner-D. C. Reiley, III

Attorney, Agent, or Firm-Oblon, Fisher, Spivak, [21] 3951143 McClelland & Maier 52 US. Cl. 148/95; 29527636153285 [57] ABSTRACT 51 Int. C1 B23k 7/00 A methd for Pmducing a casting wherein the [58] Field of g 148/9 5 164/69 is solidified in a continuous casting machine and treated by medium scarfing while maintaining the sur- 164/70 29/5275 5276 5277 face temperature at 500 to 900C, and thereafter, [56] References Cited cooled forceably to bring the surface temperature below 400C. UNITED STATES PATENTS 3,231,430 1/1966 Krieger et al. l48/9.5 x 6 Claims, 1 Drawing Figure CONTINUOUS CASTING menus CONTINUOUS FIRST COINEYOR MACHINE IEUUH SCARFER SECONDCCQNEIUR 7 COOLING IECMNISH PATENTEDJUN 17 mm a 3 8 9016 CONTINUOUS CASTING MACHINE FIRST CONVEYOR COOLING MECHANISM METHOD AND APPARATUS FOR PRODUCING A CASTING HAVING A SATISFACTORY SURFACE WITH A CONTINUOUS CASTING OPERATION BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for producing a casting and more particularly to a method and apparatus for producing a casting having improved surface characteristics obtained by a continuous casting operation.

2. Description of the Prior Art Recently, continuous casting apparatus has been accepted for practical use as the alternative of the former ingot casting-blooming mill process. As to castings which have generally been produced with a continuous casting apparatus, it has been found that various sur face defects are created due to a slight change in the operating condition of the continuous casting apparatus, namely such as an oscillation mark up to about 2.5 mm in depth corresponding to the oscillating movement of the mould, slag inclusion due to nonmetallic content resulting from composite slag added to the mould (mould filling material) or loss melting loos of refractory material of the ladle, formation of a pinhole or blowhole located just under the surface of the cast ing, generated together with the increase in amount of oxygen included in molten steel, and the formation of a longitudinal or transverse crack in the casting.

It is difficult to control or bring to zero the generation I of surface defects in continuous casting apparatus,

namely because the generation of these defects results from a slight change in the operating condition of the continuous casting apparatus as above mentioned, such that the generation of such defects is considered to be inevitable because it is extremely difficult to maintain at all times the same operating conditions in a continuous casting apparatus on a large commercial scale to carry out mass production in a stable state.

Some of such surface defects may be removed in a succeeding rolling process, but slag inclusion and surface cracks (longitudinal and transverse) have a direct effect on the surface property of steel plate after a rolling operation, such that it is necessary to remove these defects to improve the surface property.

Heretofore, when it was intending to produce a casting having satisfactory surface properties with a continuous casting operation, the casting solidified in a continuous casting machine was cooled and subjected to cold scarfing, surface examination and partial treatment of the surface by means of machining. That is, because a casting having satisfactory surface characteristics can not be obtained without using a cooled casting, for example, when producing a casting for sheet steel,

the surface of the casting must be examined carefully,

such examination and surface work in order to satisfy the examination must be based on the casting having been cooled.

Scarfing of a casting at l000l 300C, so called hot scarfing, is well known. This is carried out in a line passing through the blooming and rolling processes of slab, in which a continuous casting operation is not used or in a rolling line of steel plate, and after heating to bring the surface temperature up to l000l300C by means of a heating furnace or soaking pit, the surface of the casting is scarfed.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to eliminate processes requiring extensive time and labor such as surface examination, partial treatment by means of machining and the like, and to produce castings having satisfactory surface properties.

Another object of the present invention is to minimize the consumption of heat required to work the surface of a casting.

Another object of the present invention is to improve the efficiency of the whole production line of casting and thereby better the productivity of the casting such that a plurality of casting machines on a unitary line may be introduced.

Briefly, in accordance with one embodiment of the present invention, these and other objects may be obtained by solidifying a casting in a continuous casting machine and treated by medium scarfing while maintaining the surface temperature of the casting at 500900C, and thereafter, cooling forceably to bring the surface temperature of the casting below 400C. The medium scarfing as used herein means applying scarfing to a casting maintained at 500900C and not carried out at a high temperature such as that of a casting taken from a heating furnace and put in a rolling line. Further, a particularly more effective surface temperature for the efficiency of the line is 700800C. With this method, the casting is not heated especially in a heating furnace or the like, and the heat contained by the casting when solidified in a continuous casting machine is utilized. Furthermore, the cooled casting is in a state of near completion with regard to the surface work. As made understandable from the above, processes requiring substantial time and labor are curtailed, medium scarfing consuming less heat as compared to cold scarfing is adopted and a casting having satisfactory surface properties may be obtained even after being forceably cooled. This is a substantial change from the former prerequisite that a casting having satisfactory surface properties can not be obtained without applying surface work exclusively on a cooled casting, and satisfactory surface properties may be obtained according to the present invention, by carrying out medium scarfing and forced cooling even when cold scarfing is curtailed thereby eliminating partial treatment.

Furthermore, when carrying out said forced cooling, the casting is cooled by a water jet to bring the surface temperature thereof below 400C within 10 minutes after the completion of medium scarfing, then in addition to the effect mentioned above, a better casting may be obtained. Forced cooling cools the casting having satisfactory properties formed by medium scarfing while preventing oxidation. The water jet blows off the oxide film, if any, and improves the cooling efficiency, thereby preventing oxidation due to the high temperature of the surface and deterioration of surface properties, due to oxidation.

Also, the device according to the present invention is constructed by assembling well known machinery which is feasible for satisfying the processes mentioned above and provided with a continuous casting machine for continuously solidifying molten steel, a medium scarfer for scarfing the casting having a surface temperature of 500900C, a cooling mechanism for forceably cooling the casting, a first conveyer for carrying the casting from the continuous casting machine to the medium scarfer, and a second conveycr for carrying the casting from the medium scarfer to the cooling mechanism.

BRIEF DESCRIPTION OF THE DRAWING A more complete appreciation of the invention will be easily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing wherein the FIGURE schematically illustrates the present invention including a continuous casting machine, a medium scarfer, a cooling mechanism, and first and second conveyors.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention, as abovementioned, is characterized by applying medium scarfing to a casting while maintaining the surface temperature of the casting, obtained with a continuous casting operation, at 500900C, and thereafter forceably cooling the casting to bring the surface temperature thereof below 400C. This is to produce a casting having satisfactory surface properties directly while the casting is hot instead of as in the former process of preparing satisfactory surface properties by means of cold working such as cold scarfing, partial treatment and the like. The reason that satisfactory surface properties can be obtained and the consumption of heat can be reduced, resides in the fact that scarfing after the continuous casting operation and forced cooling are carried out in a special temperature range. The cause of the present inventions obtaining satisfactory surface properties, rapid speed of treatment and effective use of heat contained in the casting, is in the selection of the proper combination of the order of continuous casting, medium scarfing and forced cooling.

The method for producing a casting according to the present invention will be described in more detail. A casting produced by a continuous casting method contains undulated uneven oscillation marks and other surface defects of various kinds in the surface. However, on the other hand, casting carried out in a continuous casting machine having a temperature of about 500-900C, and when used to produce steel plate using a casting prepared by carrying the casting of a high temperature directly to a medium scarfer to remove the surface defects thereof, utilizing effectively the heat contained in the casting of high temperature and cooling naturally to a room temperature after applying scarfing work all over the peripheral surface of the casting, surface flaws caused by the property of the surface of the casting were generated on the surface of the steel plate. By examining the cause thereof, it has been found that as the casting was scarfed under a high temperature, the surface of the casting after scarfing work was oxidized, and therefore the surface of the casting was covered with oxide film, so that surface flaws which could not be removed by scarfing work could not be discovered by succeeding examination. It has also been found that this condition caused the flaws in the product, and when various examinations were carried out based thereon, it has been found that the generation of oxide film on the surface of the casting may be controlled by forceably cooling the casting pre pared with application of scarfing work within ten minutes after the scarfing work and rapidly cooling the casting to bring the surface temperature thereof below 400C. Scale generated momentarily made easier the detection of the surface flaws which could not be removed by scarfing work and therefore the removal of the surface flaws during the examination process was perfected'lt is therefore a prerequisite for the present invention to scarf the peripheral surface of the casting and thereafter to forceably cool the casting. In a method for producing a casting according to the present invention, what is to be noticed particularly is that the speed of treatment of casting can be optimized by utilizing the heat contained in the casting produced by a continuous casting apparatus for scarfing work and also reduction of operating cast may be expected. For example, as compared to scarfing work formerly carried out while cold, when depending on the present invention, it is possible that the treatment speed thereof is increased 2-2.5 times and the operating cost (consumption of fuel) is reduced to about one-half, and an example thereof is shown in Table I.

TABLE 1 method of former method this invention Working speed l0 m/min. 20 m/min. Consumption of oxygen (per l l m lton 5.5 m /ton ton of casting) Consumption of propane (per 1 kg/ton 0.5 kg/ton ton of casting) Furthermore, when a casting is produced with a continuous casting apparatus according to the present invention the working cast in scarfing work may be reduced more by applying several percents of rolling reduction to the casting in a continuous casting apparatus. Namely, when the casting is subjected to several percents of rolling reduction in a continuous casting apparatus, oscillation mark in the surface of the casting disappeared in consequence of plastic deformation of the casting thereby a relatively smooth surface is presented, and fine cracks (longitudinal and transverse) existing in the surface are reduced considerably in depth by the rolling reduction. As the result thereof, compared with the case in which surface of the casting is subjected to scarfing work without applying rolling reduction, the surface flaws of the casting may be removed completely with a relatively small amount of scarfing work and therefore a casting having satisfactory surface properties may be obtained.

Hereunder, the present invention will be described referring to concrete embodiments with reference to the drawing.

EMBODIMENT I An Al killed steel ofC 0.l0%, Mn O.20O.60%. P 0.30%, S 0.30 and Al 0.020-0.060% was continuously cast into a slab of 250 X 2000 mm in section with the continuous casting machine 1 as the matter of steel plate for sheet steel, and was cut into a length of 10 m. This slab (casting) was conveyed immediately to the medium scarfer 2 by the first conveyor 4 and supplied thereinto. The surface temperature of the slab was maintained at 5()0900C. In the scarfer 2 the slab was scarfed and immediately thereafter the slab was carried to the cooling mechanism 3 by the second conveyor 5. The slab was then foreeably cooled to bring the surface temperature thereof below 400C, and furthermore, cooled nearly to room temperature. Thereafter, when sheet steel was produced using the slab after normal treatment and examination, a sheet steel of excellent surface properties was obtained.

In this embodiment, as the heat presenting a temperature of 500900C of the slab solidified in the continuous casting machine 1 was utilized effectively for scarfing work in the medium scarfer 2, the treating speed thereof could he 20 m/min. about double as compared with former cold scarfing. moreover, the consumption of fuel could be reduced about one-half.

EMBODIMENT 2 A slab 200 X 1800 mm in section Al killed steel having a composition equal to the embodiment l was continuously cast, the slab was deformed by a rolling reduction of mm in the casting operation while rolling with pinch rolls of the continuous casting machine 1 or guide rolls in the secondary cooling zone. The casting was cut into a length of 10 m, and while the surface temperature was maintained at 500-900C the cut casting was supplied into the medium scarfer 2 by the first conveyor 4. In the medium scarfer 2 the surface of the casting was worked to scarf 1.5 mm in depth, and immediately thereafter, the casting was conveyed to the cooling mechanism 3 by the second conveyor 5. Forced cooling by means of a water jet was carried out and thereby the casting was cooled to bring the surface temperature thereof below 400C.

The casting was further cooled to room temperature, and then when the surface of the casting was examined, surface flaws could not bcfound for practical consideration, and the surface properties were very-satisfactory. When sheet steel was produced using the casting with a normal rolling process, an excellent sheet steel having no surface flaws caused by the surface properties of the casting could be obtained.

Medium scarfing performed with the surface temperature of the casting at 500-900C, not only brought about no damage caused by rapid heating as in cold scarfing, but may also be adapted for a wide variety of slabs. In the process of a method according to the present invention, it is not required to provide a heating fur- 6 nace for raising the temperature of the casting to apply scarfing work, and also, forced cooling after scarfing prevents generation of oxide film and provides satisfactory surface properties.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is to be understood therefore, that within the scope of the appended claims the present invention may be practiced otherwise than as specifically described herein.

I claim:

I. A method for producing a casting having satisfactory surface properties in the step after a continuous casting operation wherein the casting solidified in a continuous casting machine is subjected to a scarfing operation while the casting is kept at a high temperature, comprising the steps:

applying a scarfing operation to the casting while the surface temperature of the casting is maintained at 700-900C. and

immediately cooling said casting to bring the surface temperature thereof below 400C.

2. A method as set forth in claim I, further compris ing foreeably cooling the casting to bring the surface temperature thereof below 400C within l0 minutes.

3. A method as set forth in claim 1, further comprising foreeably cooling said casting with a water jet.

4. A method as set forth in claim 1, further compris ing subjecting the casting to rolling work before applying the medium scarfing operation.

'5. A device for producing a casting having satisfactory surface properties, comprising a continuous casting machine for continuously solidifying molten steel, a medium scarfer for scarfing said casting at 700-900C in surface temperature, a cooling mecha nism for cooling said casting, a first conveyor for carrying said casting from the continuous casting machine to the medium scarfer, and a second conveyer for carrying said casting from the medium scarfer to the cooling mechanism.

6. A device as set forth in claim 5, wherein a unitary medium scarfer and cooling mechanism are incorporated into a continuous casting machine for a plurality of strands. 

1. A METHOD FOR PRODUCING A CASTING HAVING SATISFACTORY SURFACE PROPERTIES IN THE STEP AFTER A CONTINUOUS CASTING OPERATION WHEREIN THE CASTING SOLIDIFIED IN A CONTINUOUS CASTING MACHINE IS SUBJECTED TO A SCARFING OPERATION WHILE THE CASTING IS KEPT AT A HIGH TEMPERATURE COMPRISING THE STESP, APPLYING A SCARFING OPERATION TO THE CASTING WHILE THE SURFACE TEMPERATURE OF THE CASTING IS MAINTAINED AT 700*-900*C, AND IMMEDIATELY COOLING SAID CASTING TO BRING THE SURFACE TEMPERATURE THEREOF BELOW 400*C.
 2. A method as set forth in claim 1, further comprising forceably cooling the casting to bring the surface temperature thereof below 400*C within 10 minutes.
 3. A method as set forth in claim 1, further comprising forceably cooling said casting with a water jet.
 4. A method as set forth in claim 1, further comprising subjecting the casting to rolling work before applying the medium scarfing operation.
 5. A DEVICE FOR PRODUCING A CASTING HAVING SATISFACTORY SURFACE PROPERTIES COMPRISING A CONTINUOUS CASTING MACHINE FOR CONTINUOUSLY SOLIDIFYING MOLTEN STEEL, A MEIDUM SCARFER FOR SCARFING SAID CASTING AT 700*-900*C. IN SURFACE TEMPERATURE A COOLING MECHANISM FOR COOLING SAID CASTING A FIRST CONVEYOR FOR CARRYING SAID CASTING FROM THE CONTINUOUS CASTING MACHINE TO THE MEDIUM SCARFER, AND A SECOND CONVEYOR FOR CARRYING SAID CASTING FROM THE MEDIUM SCARFER TO THE COOLING MECHANISM.
 6. A device as set forth in claim 5, wherein a unitary medium scarfer and cooling mechanism are incorporated into a continuous casting machine for a plurality of strands. 